Wireline Issue 45 - Summer 2019

S ubsea wells are a paradox – at least according to Helix Energy Solutions Group’s David Carr. They are in general among the most expensive wells in the world to drill, often in the harshest of environments and most remote areas of the world. “The paradox,” Carr explains, “is that although they are typically very prolific, they generally have the lowest recovery factor, primarily due to the fact that intervening on such wells is incredibly expensive, as it traditionally requires a large deepwater drilling unit to gain well access for such work.” The topic is a timely one, not just as the industry begins in earnest to grapple with the extent of decommissioning on the UK Continental Shelf (UKCS) – where subsea wells make up around 40% of the well stock expected to be decommissioned over the next decade – but in extending field life through workovers as well. Reducing the complexity and expense of subsea intervention operations is therefore critical to lowering operating expenditure and improving recovery over the long term. Rigless well intervention, in which smaller vessels and light well access technology are used to perform well operations, avoiding the need for a larger drillship or rig and associated riser pipework, is a key enabling technology. Helix Energy Solutions Group (ESG) is a pioneer in this field. The company made its entrance into the UK North Sea when it performed the world’s first riserless well intervention operation from the dive vessel MSV Seawell at the BP-operated Magnus field in 1987. This ground-breaking project paved the way for a whole new industry to arise – developing vessels, equipment and techniques to economically enhance, repair and ultimately decommission subsea wells. Following Helix’s advances in the light well intervention field, companies like TechnipFMC, in partnership with Island Offshore and Altus Intervention, have expanded the use of riserless light well intervention vessels (LWIV) using similar technologies. Helix however, has remained at the forefront, and still operates two vessels in the UK with unique characteristics – both the MSV Seawell and Well Enhancer LWIVs are capable of conducting well interventions using riserless technology while simultaneously performing saturation diving operations, an activity that is often essential with older subsea tree infrastructure. Carr, a senior vice president at Helix Well Ops UK, adds: “Many of these North Sea trees have been producing since the 1980s and in many cases are past their design life. Working them over with a rig would mean landing over 150 tonnes of [blow-out preventer] BOP and marine riser onto them, which is generally impossible. A riserless package – weighing from just 30 tonnes – combined with diving support is often the only way to maximise economic recovery from these older assets.”

Join the Q Although its name may have been made in the North Sea, much of Helix’s recent expansion has been concentrated in the US Gulf of Mexico and Brazil. It was this environment that spurred the development of its Intervention Riser System (IRS) for deepwater operations, where asphaltene production from high-volume wells frequently requires the deployment of coiled tubing to enter wells to clear blockages. Deployment of the IRS also led to the development and construction of the world’s first dedicated rigless intervention vessel, the Q4000 (the same vessel that would later cap the Macondo well following the Deepwater Horizon disaster). This in turn led Helix to develop Brazil’s first dedicated rigless intervention vessels, the sister ships Siem Helix 1 and 2, currently under a multi-year contract for Brazil’s Petrobras. The national oil company recently awarded Helix with the ‘2018 Supplier of the Year Award for Operation of Maritime Rigs’ – a notable achievement for the team in the first year for which they were eligible. While Helix has expanded global operations, the Seawell and Well Enhancer have remained stalwarts of the North Sea sector, Carr notes, the former undergoing a £58 million refit in 2016. More than 30 years on, the innovation that started at Magnus in 1987 will come full circle when Helix intends to introduce its new riser-based intervention vessel, the Q7000. “This is a culmination of the technologies and learning from across the world, distilled into a unit that is conceived and specified for the North Sea,” he continues. “We created a vessel that can take on the well access challenges of the west of Shetland zone, as well as being able to deal with central North Sea environments down to just 80m.” “This is a culmination of the technologies and learning from across the world, distilled into a unit that is conceived and specified for the North Sea.”

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